Minority carrier lifetime and iron concentration measurements on p-Si wafers by infrared photothermal radiometry and microwave photoconductance decay (original) (raw)
Related papers
Applied Physics Letters, 1996
A theoretical model for the photothermal radiometric signal from semiconductors of finite thickness has been used to measure simultaneously the carrier diffusion coefficient, carrier lifetime, and surface recombination velocity of FZ Si wafers with very long bulk carrier lifetimes ͑industrial microelectronic grade͒. The results showed the importance of accounting for the finite thickness of the substrate in obtaining accurate measurements of these parameters using the entirely noncontacting radiometric approach.
Impact of Fe and Cu Contamination on the Minority Carrier Lifetime of Silicon Substrates
Journal of The Electrochemical Society, 1996
The effects of trace amounts of Fe and Cu in p-and n-type silicon were investigated with microwave photoconductance decay and surface photovoltage. The wafers received controlled amounts of surface contamination of Fe and Cu that are relevant for ultralarge scale integrated technologies. The substrate doping type has a strong impact on the effect of the metallic impurities. Fe, as expected, strongly degrades the minority carrier lifetime of p-type substrates. On the other hand, the impact of Fe on n-type silicon is at least one order of magnitude lower than on p-type. In contrast, Cu is highly detrimental to n-type material, but has no significant impact on the minority carrier properties of p-type silicon for the contamination levels studied.
physica status solidi (a), 2001
Subject classification: 72.20.Jv; 73.40.Mr; S5.11 Laser infrared photothermal radiometry (PTR) was used as an analytical technique to measure the electronic transport parameters of p-Si wafers oxidized and thermally annealed under positive or negative external bias applied to the back surface. It was found that, following Fe contamination and recombination lifetime t e , degradation in the oxidation and thermal-anneal furnace, both polarities of the external field result in significant minority carrier lifetime improvement, as well as in strong changes in the front-surface recombination velocity S 1 , of the samples, compared to a zerobias annealed reference sample. A qualitative model involving the passivating action of positive mobile ions (protons) trapped at the oxide-Si interface was advanced to explain the relative relations S 1 (+) > S 1 (0) > S 1 (--) . The lifetime relations t e (+) > t e (--) > t e (0) obtained through both PTR and electrolytical metal tracer (ELYMAT) measurements were explained in terms of the relative abilities of positive and negative applied electric fields to prevent heavy metal ions from diffusing into the Si bulk and compromising the lifetime.
Contamination monitoring of Si wafers using photocarrier radiometry
Journal de Physique IV (Proceedings), 2005
The ability of photocarrier radiometry to perform lifetime imaging of Si wafers is reported. The methodology involves PCR imaging of the sample at one or several frequencies with frequency scans performed at positions of interest. The frequency scans are fit to theory to obtain carrier lifetimes that are used in conjunction with the PCR amplitude and phase images to produce lifetime images. The direct correlation between contamination and carrier lifetime in Si allows for generation of contamination/defect concentration images in a completely non-contact, preparation free process suitable for in line monitoring of contamination.
1996
Laser-induced and frequency-scanned infrared photothermal radiometry was applied to a crystalline-Si photoconductive device, and to polysilicon thin-film photoconductors deposited on oxidized Si substrates by an LPCVD method. A detailed theoretical model for the radiometric signal was developed and used to measure the free photoexcited carrier plasma recombination lifetime, electronic diffusivity and surface recombination velocity of these devices, with the simultaneous measurement of the bulk thermal diffusivity. A trade-off between detectivity/gain and frequency-response bandwidth was found via the lifetime dependence on the wafer background temperature rise induced by Joule-heating due to the applied bias. This effect was most serious with the bulk-Si device, but was limited by the high resistivity of the LPCVD thin-film devices. In the case of the bulk-Si device, the results of photothermal radiometry were compared with, and corroborated by, frequency-scanned photocurrent measurements. More sophisticated analysis was shown to be required for the interpretation of the polysilicon photoconductor frequency-responses, perhaps involving the fractal nature of carrier transport in these grain-structured devices.
2000
The physical principles and application case studies of the novel diagnostic technique of laser infrared photothermal radiometry ͑PTR͒ of semiconductors are presented. Following superband gap optical excitation, the signal consists of two contributions, one due to the de-exciting carrier density ͑plasma wave͒ and another from direct absorption and heating of the lattice ͑thermal wave͒. Multiparameter fits to frequency-domain amplitude and phase data have been developed to reliably measure recombination lifetime, surface recombination velocities ͑front and back surface͒, electronic, and thermal diffusivities. Applications case studies are presented, which demonstrate that lifetime measurements using PTR provide a most sensitive, convenient, and nonintrusive, remote industrial semiconductor metrology. The new metrology combines the features of several laboratory and commercial techniques currently available for industrial wafer ͑substrate and process͒ characterization ͑e.g., thermoreflectance, microwave reflectance, and surface photovoltage͒. The technology is capable of being used as a sensitive control of ion implantation, contamination monitor during oxidation and wafer cleans, and photoexcited carrier recombination lifetime measurements.
Dynamic carrier lifetime imaging of silicon wafers using an infrared-camera-based approach
Applied Physics Letters, 2008
We present a calibration-free dynamic infrared carrier lifetime mapping technique, yielding images of the carrier lifetime of multicrystalline silicon wafers within seconds. Images of the infrared emission of the sample under test are taken directly after switching on a monochromatic illumination source and after steady-state conditions have been established in the sample. Making use of the proportionality between the infrared emission and the free carrier density inside the sample, the carrier lifetime is calculated from the signal ratio of these two images by an analytical method. We achieve an excellent agreement when comparing our results with carrier lifetime mappings obtained by the microwave-detected photoconductance decay technique.